The present invention relates to a vehicle suspension apparatus with a hydraulic height control function.
A known conventional vehicle suspension apparatus comprises height control fluid spring chambers arranged between the respective wheels and the vehicle body, a fluid supply means for supplying a fluid from a fluid source to the fluid spring chambers through corresponding fluid supply control valves, a fluid exhaust means for exhausting the fluid from the fluid spring chambers through corresponding fluid exhaust control valves, a height sensor for detecting the vehicle's height from the ground (hereinafter referred to as the vehicle's height), and a height control means for comparing the height detected by the height sensor with a target height and controlling the supply or exhaust control valves so as to make the detected height equal to the target height.
In a conventional vehicle suspension apparatus of this type, in the case of increasing the vehicle height so as to decrease the virtual distance to jack-up the vehicle upon replacement of wheels or to simplify attachment/detachment of tire chains, the height control means sets the target height to a high height which is higher than the normal height, and controls said valves so as to make the detected height equal to the target height.
According to the height control technique described above, however, the following drawback is presented. When the height is to be increased, the height detected by the height sensor must be discriminated as higher or lower than the target height, thereby complicating the structure of the height sensor. For example, in order to set the height to a height higher than the high vehicle's height, the target height is set at an extra high height. At the same time, the height sensor must have a function for discriminating whether or not the detected height is higher than the extra high height. As a result, the structure of the height sensor is more complicated, thus resulting in inconvenience.